Mechanical Properties and Rapid Sintering of WC-BN-Al Composites

Abstract

Tungsten carbides are quite attractive for their superior properties, e.g., high melting point, high hardness, high thermal and electrical conductivities, and relatively high chemical stability. Tungsten carbides with a binder metal, for example Co or Ni, are mainly used to produce cutting tools, nozzles and molds in the composite form. But these binder materials show inferior chemical characteristics compared to the tungsten carbide phase. There has been enormous interest recently in finding alternative binder phases because of the low corrosion resistance and the high cost of Ni or Co. Al has been reported as an alternative binder for WC and TiC, since Al is less expensive and shows a higher oxidation resistance than Ni or Co. Nanostructured WC-BN-Al composites were rapidly sintered using high-frequency induction heated sintering (HFIHS). The microstructure and mechanical properties (fracture toughness and hardness) were investigated by Vickers hardness tester and FE-SEM. The HFIHS method induced very fast densification, nearly at the level of theoretical density, and successfully prohibited grain growth, resulting in nano-sized grains. The fracture toughness was improved by consolidation facilitated by adding Al to the WC-BN matrix. The 5vol % Al added WC-BN composites showed higher mechanical properties (hardness and fracture toughness than the WC-BN composite.